The present invention relates to a camera in which a film back can be attached to and detached from a camera body, and an exchangeable film back, and particularly to a film back exchangeable camera and an exchangeable film back which have a film shielding function.
In a film back exchangeable camera in which a film back can be attached to and detached from a camera body, a shielding means is used in order to optically shield an interior of the film back when the film back is not attached to the camera body. A typical shielding means, which is widely used, is arranged such that a shielding plate is inserted into a slit provided to the film back. The shielding means of this type imposes a troublesome work since a photographer must detach the shielding plate after the film back is attached to the camera body. Further, the photographer is likely to fail to detach the shielding plate. The film back exchangeable camera is generally designed to establish a release lock state to inhibit photographing in a case where the shielding plate is not detached. However, in this constitution, the photographer is not aware that he has failed to detach the shielding plate until the release operation is actually performed. Therefore, many shutter release moments are frequently missed. Further, the shielding plate separate from the film back is likely to be lost.
The invention has been made in view of the above problems, and an object of the invention is to provide a film back exchangeable camera and/or an exchangeable film back, which can reduce a load on the photographer in connection with the shielding function of the film back and which is free from the lost of the shielding member.
In order to attain the above-noted object, the invention provides an arrangement for selectively establishing a shielding state and a light transmissible state (photographable state) with a shielding member built in a film back, according to attachment and detachment of the film back to a camera body.
A preferred embodiment of the present invention is a camera having a camera body and a film back that can be attached to and detached from the camera body The camera includes: an aperture formed in the film back, through which photographing light flux passes; a film supplying mechanism that moves a film at a rear of the aperture; a shielding member, which is built in the film back and located movably in front of a film running surface in the rear of the aperture and which is movable between a shielding state where a film is not exposed to light and a light transmissible state where the shielding is released and the film exposure is permitted; a shielding member driving mechanism for driving this shielding member from the shielding state to the light transmissible state; a forward/reverse rotation motor; and a motor linking switch mechanism by which the forward/reverse rotation motor is switched to be linked with the film supplying mechanism and the shielding member driving mechanism according to the forward rotation and the reverse rotation of the forward/reverse rotation motor. In the camera, the film supply is executed by the forward rotation of the forward/reverse rotation motor, and the shielding member is actuated from the shielding state to the light transmissible state by the reverse rotation of the same. According to this constitution, since the shielding member can be operated from the shielding state to the light transmissible state by the driving force of the motor used for the film supply, the load that the photographer operates the shielding member can be eliminated. Further, since the shielding member is built in the film back, there is no fear that it may be lost. The film supply executed by the forward rotation of the forward/reverse rotation motor is taken, for example, as a film winding-up.
It is desirable in this film back exchangeable camera that a shielding member energizing means for energizing the shielding member to the shielding state is provided. Under this constitution, when the light transmissible state is switched to the shielding state, the load that the photographer operates the shielding member can be also eliminated. Further, by the energizing means, quick shielding can be performed; and even if the motor or the power source malfunctions, the shielding member is operated without any problems. Therefore, the undesired film exposure can be prevented.
Regarding the concrete constitution in which the shielding member is built in the film back, the following constitution is preferable. The shielding member is constituted as a curtain-shaped member having a light transmissible portion of a size corresponding to a size of the aperture of the film back. Further, the film back includes a first winding shaft to which one end portion of the shielding member is fixed and which is rotatingly energized by the shielding member energizing means in a direction where the shielding member is wound up; and a second winding shaft to which the other end of the shielding member is fixed and which is rotated by the reverse rotation of the forward/reverse motor in a direction where the shielding member is wound up. And, when the shielding member is wound up on the first winding shaft, the light transmissible portion retreats from the forward position of the film running surface and the film back enters into the shielding state; and when the shielding member is wound up on the second winding shaft, the light transmissible portion is located in the front of the film running surface and the film back enters into the light transmissible state.
It is preferable that the motor linking switch mechanism is provided with a planet gear selectively meshing with a gear on the film supplying mechanism side and a gear on the shielding member driving mechanism side according to the forward rotation and reverse rotation of the forward/reverse rotation motor.
It is further desirable that in the above-described film back exchangable camera, there are provided lock means for locking the film back in the camera body in a state where the former is mounted on the latter; and a lock linking keeping means which keeps a lock state where the film back is locked in the camera body by the lock means, so that even if the reverse rotation of the forward/reverse rotation motor is stopped, the shielding member is kept in the light transmissible state, and in case of an unlock state of the lock means, keeping is released and the operation of the shielding member from the light transmissible state to the shielding state is permitted. This constitution is particularly effective in case that the-shielding member is energized in the shielding direction by the above shielding member energizing means. During photographing with the film back attached to the camera body, even if the forward/reverse motor is not driven, the light transmissible state can be kept; and also the shielding member can be switched to the shielding state as soon as the lock of the film back is released.
The lock means can be composed of a fitting hook provided to the camera body, which enters into the film back when the film back is attached; a movable lock member, which. can be moved in a lock position Where it is fitted to the fitting hook and in an unlock position where fitting is released, and which is provided in the film back; and lock member energizing means for energizing the movable lock member to be moved to the lock position. The lock linking keeping means can be composed of a cam gear which rotates in a predetermined direction when it is linked with the reverse rotation of the forward/reverse rotation motor thereby to operate the shielding member to the light transmissible state, and which is driven and rotated in the opposite direction to the direction at the motor linked state when the shielding member is operated from the light transmissible state to the shielding state; and a fitting lever which can be rotated between a fitting position where the driven-rotation of the cam gear in the opposite direction to the direction at the motor cooperating time is restricted and a fitting release position where the rotational regulation is released, and which is kept in the fitting position when the movable lock member is in the lock position, and rotated to the fitting release position by the movement of the movable lock member in the unlock direction. In this case, the fitting lever can be controlled with the simple constitution if the lock member and the lock linking keeping means are so constituted that when the cam gear rotates in linking with the reverse rotation of the forward/reverse rotation motor, the fitting lever is pressed by the cam gear and rotated to the fitting release position, and when the cam gear performs one rotation, the fitting lever returns to the fitting position.
In case that the lock means and the lock linking keeping means are constituted as described above, it is preferable to provide a first switch for detecting the fitting position and fitting release position of the fitting lever; a second switch for detecting the lock position and unlock position of the movable lock member; a third switch for detecting the entry of the fitting hook on the camera body side into the fitting position to the movable lock member; and control means which, on condition that the fitting position of the fitting lever, the lock position of the movable lock member, and the entry of the fitting hook are simultaneously detected by these switches, executes the reverse rotation of the forward/reverse rotation motor and operates the shielding member to the light transmissible state. By this constitution, only in case that the film back is exactly attached to the camera body, the shielding state can be released, so that the occurrence of the unprepared shielding release operation can be prevented.
The invention also relates to an exchangeable film back that can be attached to and detached from a camera body. This film back comprises an aperture through which camera light flux passes; film supplying mechanism that moves a film at the rear of the aperture; a shielding member, which is movably located forward of a film running surface in the rear of the aperture and which can move from a shielding state where the film is not exposed to light and to a light transmissible state where the shielding is released and the film exposure is permitted; shielding member driving mechanism for driving this shielding member from the shielding state to the light transmissible state; and motor linking switch mechanism which is driven by rotation of a forward/reverse rotation motor, and selects the film supplying mechanism or the shielding member driving mechanism according to its forward rotation and reverse rotation thereby to actuate the selected mechanism. Andy this film back is characterized in that the film supply is executed by the forward rotation of the forward/reverse rotation motor, and the shielding member is actuated from the shielding state to the light transmissible state by the reverse rotation of the same. In this exchangeable film back, also, it is desirable that a shielding member energizing means for energizing the shielding member to the shielding state is provided similarly to the aforesaid camera.
The present disclosure relates to the subject matter contained in Japanese patent application No. 2000-4429 (filed on Jan. 13, 2000), which is expressly incorporated herein by reference in its entirety.